Video narration
Why does a melted ice cube never suddenly become the same perfect cube again? It's tempting to say entropy just means mess, but that shortcut misses the point. In your drink, heat moves between the cold ice, the warmer liquid, and the surroundings. As that energy spreads, it can be shared among tiny particles in more ways. Entropy measures how many microscopic arrangements are possible-especially when energy is spread out. The second law of thermodynamics says that for an isolated system, total entropy does not decrease. One small area can become more ordered, like ice forming, but only while the surroundings gain even more entropy. So the melted cube doesn't reverse because nature forbids every reversal. It's overwhelmingly unlikely for all that spread-out energy to gather into one arrangement at once. That's why your drink stays melted: entropy makes the perfect ice cube an extraordinarily unlikely destination.